Data compressing system



P 23, 1965 R. N. SKALWOLD 3,209,079

DATA COMPRESSING SYSTEM Filed April 3, 1962 IN VEN TOR. eaazierm drab a0BY WW MZZMWX United States Patent 3,209,079 DATA COMPRESSING SYSTEMRobert N. 'Skalwold, 705 Clinton St, Rome, N.Y. Filed Apr. 3, 1962, Ser.No. 184,864

. 9 Claims. (Cl. 179-'100.2) (Granted under Title 35, US. Code (1952),see. 266) The invention described herein may be manufactured and used byor for the United States Government for governmental purposes withoutpayment to me of any royalty thereon.

This invention relates to a recording system for the recording of speechor other message waves or pulses of which only selected signal fragmentsneed be retained. The novel system disclosed herein provides for therecording of said signal fragments in a contiguous manner therebyeliminating the need to record the no-signal period that exists betweenthem. Said recording system is also adapted to play back the recordedsignal fragments in their proper time-phase relationship.

There are many communication systems currently in use whereincomprehensible intelligence is transmitted by subdividing the speechwave on a time basis, discarding certain of the subdivided fragments,and transmitting only the intervening fragments. It has been establishedthat speech and other audio frequency information transmitted in thismanner can be understood and utilized even though a considerable portionof the speech or information is removed in the process.

Present means for recording audio signals from which certain portionshave been removed are costly and technically difficult. The use of afast acting clutch which will start and stop the recording tape at therequired bit speed is illustrative of the present state of the art. Thismethod is unsatisfactory in that it requires the starting and stoppingof the tape motion almost instantaneously at audio frequency rates.Alternatively, continuous recording of both signal and no-signal periodsresults in an extravagant Waste of tape and requires recording meanshaving the capacity to accommodate much larger tape reels.

Applications of my invention in which the resulting economy of recordingmedium is of paramount importance include, enter alia, the continuousmonitoring and permanent recording of conversations and messages; therecording of variations or strain gauge outputs in various scientificinvestigations, such as aircraft testing, where recorded bits wouldprovide representative sampling and reduce the magnitude of data to beexamined; and the recording of telemetered instrument readings.

Accordingly, it is a principal object of my invention to provide a novelmeans for recording intermittent fragments of speech Waves or otherperiodic discontinuous signals adjacent to each other thereby makingoptimum, economical use of the recording medium.

It is a further object of my invention to provide a recording meanswhereby periodic signal fragments may be recorded in a continuous mannerin combination with means for reproducing said signal fragments in theirproper time phase and interval.

It is a further object of my invention to provide a method wherebyrecordings of speech, electrical outputs, monitored radio transmissionsand other similar intelligence can be made in such a way that therecorded information is compressed, thereby vastly reducing the amountof tape or other material required for recording it.

It is a further object of my invention to provide a novel recordingmeans whereby information in the form of intermittent, periodic, signalfragments may be recorded on foreshortened electromagnetic tape, groovedrecords or photo-sensitive film simply and with reliable components.

Patented Sept. 28, 1965 These and other advantages, features and objectsof the invention will become more apparent from the followingdescription taken in connection with the illustrative embodiment in theaccompanying drawing, wherein:

FIG. 1 is a diagrammatic representation illustrating one physicalarrangement of an embodiment of my invention; and

FIG. 2 is a schematic wiring diagram of said embodiment of my invention.

Referring now to FIG. 1, electronic switch 4 is synchronized withrecording transfer wheel 6 in such a Way that it is on, allowinginformation from input 12 to be recorded on recording material 7 for onecomplete rotation of transfer Wheel 6. Electronic switch 4 is then offfor a number of complete revolutions of transfer wheel 6 correspondingto that portion of the input signal which is to be rejected. Forexample, if the off to on or reject to record radio is three to one,then electronic switch 4 would pass the input signal during onerevolution of transfer wheel 6 and reject the signal during threerevolutions of said transfer wheel.

Transfer wheel 6 is driven by driving motor 16. Said transfer wheelcarries on its outer edge a width of thin magnetic recording material 7in the plane of the transfer wheel such that recording head 8 can beplaced on one side and pick up head 9 on the other side. Both recordinghead 8 and pick up head 9 are conventional, combined,recording-pickup-erasing heads, and while each may perform the functionof recording, detecting or erasing according to the instant function ofthe present invention, they have been designated recording head andpickup head, respectively, in the interest of clarity of description.The tape need only be of a type which has a base that would allowpick-up or recording therethrough. The type of base would affect thepower requirements of the recording and pick-up system.

The relative actions of transfer Wheel 6, recording head 8, and pick uphead 9 follows.

Electronic switch 4 passes signal fragments to amplifier 5, wherein itis amplified and passed to recording head 8. Recording head 8 recordssaid signal fragment on the magnetic recording material on recordingtransfer Wheel 6. Electronic switch 4, being synchronized with recordingwheel 6, passes a signal fragment, the duration of which is exactlyequal to the length of time required for recording wheel 6 to make onecomplete revolution. One signal fragment has thus been recorded onmagnetic recording material 7, and occupies the entire circumference oftransfer wheel 6.

Pick up head 9 is suitably mounted on rotatable arm 10, and is driven byany suitable speed reducing means in such a way as to make one completecircuit of magnetic recording material 7 during the period from thestart of recording of one signal fragment to the start of recording thenext. Thus, if the off to on ratio is three to one, pick up arm 10,carrying pick up head 9, Would make three revolutions while magneticrecording material 7 being disposed on the outer circumference oftransfer wheel 6 makes four revolutions. Pick up head 9 detects thesignal fragment which has been recorded on magnetic material 7 byrecording head 8. The output of pick up head 9 is applied, by theconventional use of slip rings 15 to recorder 14 through amplifier 17.Inductive or capacitive coupling may be substituted for slip rings.Recorder 14 is synchronized with the transfer Wheel 6 and pick up head 9by means of a conventional speed reducer. Pick up head 9, in addition todetecting the signal recorded on recording material 7, serves to erasethe signal, thereby leaving recording material 7 ready to receive asubsequent recording from recording head 8 during the next cycle ofoperation. Alternatively, the recording 3 head could serve as an erasingmeans when it is recording its next bit on the recording material 7.

As previously explained, recording head 8 records a signal fragment ontransfer wheel 6 only during every fourth revolution of said wheel. Pickup head 9 detects the signal from recording material 7 continually.

Appropriate speed reduction for producing the desired speed ratios maybe achieved, as shown in FIGURE 1, by applying power from motor 16 bymeans of gearing to a gear on shaft 43 to which transfer wheel 6 isfixed and to a gear on outer, hollow concentric shaft 44 to which pickup arm is secured. The appropriate speed ratio between transfer wheel 6,pick up arm 10 and recorder 14 may be achieved by means of gearing fromshaft 43 to the tape speed mechanism, for example, by means of the bevelgears shown in FIGURE 1.

To clarify and explain one cycle of operation of my invention thefollowing description and sequence of operation is made with referenceto the aforementioned, arbitrary three to one, off to on, ratio.Recording head 8 record for one complete rotation of transfer wheel 6and then stops due to the action of electronic switch 4. One signalfragment or bit has now been recorded.

When recording stops, pick up head 9 is directly opposite recording head8 at a position of dead space and begins detecting data from therecording material. Due to pick up head 9 traveling at a slower ratethan transfer wheel 6, transfer wheel 6 makes four revolutions duringthe time it takes pick up head 9 to make three revolutions. Thus,magnetic recording material 7 on transfer wheel 6 passes under pick uphead 9 completely one time during one cycle of operation. At the instanttransfer wheel 6 has completed four revolutions, pick up head 9, whichhas completed three revolutions, is positioned exactly oppositerecording head 8, and recording again commences and proceeds for aperiod of time equal to one revolution of the transfer wheel. Pick uphead 9 is detecting the recorded data continually, but because it ismoving in the same direction as transfer wheel 6 and at a slower rate,it detects information at a rate slower than it was delivered. Thus, thecycle is repeated.

The information detected by pick up head 9 is recorded on recordingmeans 14 which is synchronized by any suitable means with the speed ofrotation of transfer wheel 6. The preferred method of recording is bymeans of a conventional magnetic tape recorder. The tape recorder speedis adjusted in relation to the speed of the pick up arm in such a manneras to take advantage of the optimum recording rate of the tape recorder,with the result that all space on the tape is utilized, even though thesignal fragments selected by electronic switch 4 are time spaced.

For telemetering the original time spacing need not be reconstructed,however, normal operation to play back or read out the recordingrequiresreversal of the recording process. The recorded signal fragmentsare fed from recording means 14 through amplifier 17 to pick up head 9which now acts as a recording head. During the succeeding fourrevolutions of transfer wheel 6, which constitute one cycle ofoperation, one signal fragment is recorded. This requires one lessrevolution by pick up head 9 than by transfer wheel 6. In the three offto one on ratio described above there would be four revolutions oftransfer wheel 6 and three revolutions of pick up head 9. At the instantpick up head 9 completes its recording cycle (three revolutions in theexample), it is directly opposite recording head 8. Recording head 8,now acting as a pick up, plays back that which had been recorded. Thisplay back period extends for only one revolution of transfer wheel 6.The signal which has been thus picked up by recording head 8 can berecorded on tape as bits followed by no signal, and can be played by anysuitable means such as through loud speakers, or recorded by pen and inkon paper, depending on the .type signal or data recorded and theoriginal purpose for making the recording.

In order to play back the compressed signal fragments originallyrecorded on recording means 14, it is necessary to synchronize themagnetic tape or other recording medium the speed of transfer wheel 6and pick up head 9. One method by which this can be readily accomplishedprovides that, when the data is recorded, a click is recorded whenrecording head 8 and pick up head 9 are adjacent. By monitoring theclicks and the position of pick up head 9, the tape can be adjusted byany suitable means.

Although an off to on ratio of three to one was used as an illustrativeexample in the foregoing description, there is no intent to restrict myinvention to this ratio. Any on to off ratio wherein the transfer wheel6 rotates an integral number of times greater than that of the transferarm 10 may be utilized.

In the description, magnetic recording material 7 was described as lyingin the plane of transfer wheel 6 at its outer edge. Other configurationswould be equally suitable, their choice being dictated by fabrication ormanufacturing considerations. Thus, the material could be placedcylindrically on the edge of the transfer wheel with the recording headand pick up head being placed inside and outside respectively.

An example of electronic means which may be employed in the embodimentof my invention described herein for providing the signal fragmentsreferred to in the above description is illustrated by the schematicdiagram of FIG. 2. The input signal is applied to the control grid of aconventional coincidence or gating pentode 27 by means of lead 48.Coincidence pentode 27 together with rotary switch 23 compriseelectronic switch 4. Rotary switch 23 is geared directly to shaft 43 oftransfer wheel 6 by means of gear 21 and idler gear 22 and ring gear 45.Conductive segments 24 and non-conductive segments 25 of rotary switch23 are so proportioned with relation to their speed of rotation as toprovide the desired on to off ratio. Contacts 26, therefore, close thecircuit by their interaction with conductive segments 24 during thedesired on period, thereby biasing the suppressor grid of coincidencepentode 27 in order to allow it periodically to conduct said inputsignal.

The signal fragments periodically appearing at the output of coincidencepentode 27 are amplified by one half of dual-triode amplifier 5. Saidamplified signal fragments are then applied to recording head 8 throughselector switch 33 which is shown in the record position. The signalfragments being recorded on transfer wheel 6 are detected by pickup head9 in accordance with the foregoing description and are then applied tothe grid of one half of dual-triode amplifier 17 by means of selectorswitch 34. Selector switch 34 is also shown in the record position. Theamplified output of dual-triode amplifier 17 is then applied torecording head 32 whereby it is permanently recorded on any desirablerecording medium. Recording heads 8 and 32 and pick up head 9 are allconventional recording pickup heads having included therein erasingcoils 35, 37 and 36 respectively. Switches 38, 39 and 40 permit erasureof the recorded information whenever required. Separate erase coilswould not be necessary where the recording action eliminates thepre-recorded signal. Also, the coincidence tube is merely a refinementand may be substituted by any mechanical or electronic switch whichwould produce the desired switching times.

Playback of the recorded information is achieved by throwing selectorswitches 33 and 34 to their playback positions. Information detected byrecording head 32 is then amplified by the other half of dual-triodeamplifier 17 and recorded on transfer wheel 6 by pickup head 9.Recording head 8 then detects the information in its proper time-phasesequence as described above in connection with FIG. 1 and applies it tothe grid of the other half of amplifier 5 through selector switch 33.The output of amplifier 5 is then applied to a loudspeaker, recordingmilliameter or other desired output means.

Although the invention has been described with reference to a particularembodiment, it will be understood to those skilled in the art that theinvention is capable of a variety of alternative embodiments within thespirit and scope of the appended claims.

I claim:

1. A data compressing system comprising means for dividing an electricalsignal into intermittent fragments, said means including an electronicswitch and a rotatable message receiving wheel having switch-actuatingsegments operatively connected thereto for causing said electronicswitch to interrupt said electrical signal periodically, means forproviding a first recording of said fragments in their normaltime-spaced relationship, and means for providing from said firstrecording a second recording of said fragments in a contiguousrelationship.

2.. The system defined in claim 1 including means for reproducing fromsaid second recording said fragments in their original spatialrelationship.

3. A data compressing system in accordance with claim 1 wherein saidmeans for dividing said intermittent fragments comprises a switchingcircuit.

4. A data compressing system in accordance with claim 1 wherein saidmeans for providing said first recording comprises a rotatable wheelhaving a recording medium disposed on the outer periphery thereof, saidwheel being synchronized with said means for dividing said electricalsignal, and a fixed recording head, said fixed recording head being inclose proximity to said recording medium and adapted to record thereonthe output from said means for dividing said electrical signal.

5. A data compressing system in accordance with claim 1 wherein saidmeans for providing said second recording comprises a rotatable member,said rotatable member being in close proximity to a rotatable wheelhaving a recording medium disposed on the outer periphery thereof anddisposed to revolve on a common axis therewith at a fractional speedthereof, a pickup head, said pickup head being disposed on saidrotatable member in close proximity to said recording medium and adaptedto detect a signal fragment recorded thereon, and a tape recorder, saidtape recorder being adapted to record the output of said pickup head.

6. In a communications system, data compressing apparatus comprising,means to sub-divide a modulated electrical wave into periodic fragments,said means including an electronic switch and means for causing saidswitch to interrupt said electrical wave periodically, means forproviding a first record of each of said fragments at preselected timeintervals, means for providing from said first record a second record ofeach of said fragments, the relative recording times of said first andsaid second records being adapted to provide a contiguous relationshipof said fragments in said second record and means for subsequentlyreproducing said fragments in their original time-spaced relationship.

7. A system as defined in claim 6 including means for erasing said firstrecord.

8. A data compressing system comprising means for providing anelectrical signal, means for cyclically obtaining segments of saidsignal, said means including an electronic switch and rotatable meansfor causing said switch to interrupt said electrical signalperiodically, said rotatable means including a data storage deviceholding intelligence in the form of a continuous train of said signalsegments, means for continuously detecting from said storage device saidsignal segments, and means for permanently recording said detectedsignal segments for subsequent reproduction in their originaltime-spaced relationship.

9. In a system for recording selected signal fragments, apparatus forpresenting said signal fragments in a timewise contiguous relationship,said apparatus comprising a recording head, a temporary recordingmedium, a pickup head wherein the relative motion between said recordinghead, said temporary recording medium and said pickup head are such thatsaid pickup head detects one complete signal fragment during thetime-interval from the commencement of recording of one signal fragmentto the commencement of recording of the next succeeding signal fragment,and electrical current interrupting means forming part of said temporaryrecording medium for periodically interrupting signal transmission.

References Cited by the Examiner UNITED STATES PATENTS 2,886,650 5/59Fairbanks et al. 179-100.2

IRVING L. SRAGOW, Primary Examiner.

9. IN A SYSTEM FOR RECORDING SELECTED SIGNAL FRAGMENTS, APPARATUS FORPRESENTING SAID SIGNAL FRAGMENTS IN A TIMEWISE CONTIGUOUS RELATIONSHIP,SAID APPARATUS COMPRISING A RECORDING HEAD, A TEMPORARY RECORDINGMEDIUM, A PICKUP HEAD WHEREIN THE RELATIVE MOTION BETWEEN SAID RECORDINGHEAD, SAID TEMPORARY RECORDING MEDIUM AND SAID PICKUP HEAD ARE SUCH THATSAID PICKUP HEAD DETECTS ONE COMPLETE SIGNAL FRAGMENT DURING THETIME-INTERVAL FROM THE COMMENCEMENT OF RECORDING OF ONE SIGNAL FRAGMENTTO THE COMMENCEMENT OF RECORDING O THE NEXT SUCCEEDING SIGNAL FRAGMENT,AND ELECTRICAL CURRENT INTERRUPTING MEANS FORMING PART OF SAID TEMPORARYRECORDING MEDIUM FOR PERIODICALLY INTERRUPTING SIGNAL TRANSMISSION.